1. Field
Embodiments of the invention relate to the field of surgical instruments; and more specifically, to surgical instruments intended for use in minimally invasive surgeries.
2. Background
Minimally invasive surgery (MIS) (e.g., endoscopy, laparoscopy, thoracoscopy, cystoscopy, and the like) allows a patient to be operated upon through small incisions by using elongated surgical instruments introduced to an internal surgical site. Generally, a cannula is inserted through the incision to provide an access port for the surgical instruments. The surgical site often comprises a body cavity, such as the patient's abdomen. The body cavity may optionally be distended using a clear fluid such as an insufflation gas. In traditional minimally invasive surgery, the surgeon manipulates the tissues by using hand-actuated end effectors of the elongated surgical instruments while viewing the surgical site on a video monitor.
The elongated surgical instruments will generally have an end effector in the form of a surgical tool such as a forceps, a scissors, a clamp, a needle grasper, or the like at one end of an elongate tube. An actuator that provides the actuating forces to control the end effector is coupled to the other end of the elongate tube. A means of coupling the actuator forces to the end effector runs through the elongate tube. To minimize the size of incision needed for the instrument access port, the elongate tube is generally of a small diameter, preferably about 6 millimeters. Thus, it is necessary that the means of coupling the actuator forces to the end effector be compact.
It may be desirable that the elongate tube be somewhat flexible to allow the surgical instrument to adapt to the geometry of the surgical access path. In some cases, the elongate tube may be articulated to provide access to a surgical site that is not directly in line with the surgical access port. It may be desirable to use wires as the means of coupling the actuator forces to the end effector because of the flexibility they provide and because of the ability of a wire to transmit a significant force, a substantial distance, through a small cross-section. However, an unsupported wire is only able to transmit a force in tension. Thus it is generally necessary to provide two wires to transmit a bidirectional actuating force. This doubles the cross-section required for the wires to pass through the elongate tube.
The wires need to have sufficient strength to provide the tension necessary to create the required forces provided by the end effector. The more tension that is required, the larger the wire cross-section must be. Inefficiencies in converting wire tension into end effector forces increases the tension, and hence the cross-section, required. Increases in the cross-section, whether because of a greater number of wires or a larger cross-section of the individual cables, increases the effect of bending the cable, such as when is passes through an articulated wrist joint, on the force being delivered by the cable. This can cause changes in the clamping pressure of a surgical end effector as the end effector is moved by an articulated wrist assembly that supports the end effector.
It is also desirable to provide electrical connections to provide an electrical current for bipolar cautery in which a tissue is cauterized by current flowing through the tissue. The two connections of opposite polarity to the tissue can be provided by the two jaws of the surgical end effector. Thus it is necessary to electrically isolate one jaw from the other and provide an insulated electrical connection from each of the two jaws to the actuator end of the elongate tube where the cautery current is supplied.
In view of the above, it would be desirable to provide an improved apparatus and method for transmitting bidirectional actuating forces through an elongate tube and applying those forces to a surgical end effector of a surgical instrument intended for use in minimally invasive surgeries that reduces the cross-section required in the elongate tube and providing electrical connections for the electrical current needed for bipolar cautery.